Polyaxial spinal stabilizer connector and methods of use thereof

ABSTRACT

A connector device for a spinal stabilization apparatus comprises a first elongated portion adapted to engage a first spinal stabilizer rod proximal to the first end of the elongated member. The first end of the first elongated portion comprises a hook shape and a ferrule and may engage the first spinal stabilizer rod within about 20 degrees of perpendicular to the spinal stabilizer rod in any direction. The ferrule is adapted to be seated within the hook shape and is further adapted to engage the first spinal stabilizer rod. The connector device may also include a second elongated portion similar to the first adapted to engage a second spinal stabilizer. The first elongated portion and the second elongated portion may be directly attached. The connector device may be used in a method of treating a patient.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. applicationSer. No. 12/856,235, filed Aug. 13, 2010, which is incorporated byreference herein, and which is a continuation of U.S. application Ser.No. 11/623,180, filed Jan. 15, 2007, now U.S. Pat. No. 7,794,478, whichis also incorporated by reference herein.

BACKGROUND OF THE INVENTION

This invention relates to fixation devices for the spinal column. Moreparticularly, this invention relates to a connector for connectingspinal stabilization rods located on the same or opposing sides of thespinal column in a spinal fixation device and associated components.Specifically, this invention relates to a connector system that allowsfor connection of spinal stabilization rods even when the rods areoriented along axis that do not intersect.

The spine is formed of a series of bones called vertebrae. There are 33vertebrae, which are grouped as cervical, thoracic, lumbar, sacral, andcoccygeal vertebrae, according to the regions of the spine they occupy.A typical vertebra consists of two essential parts, an anterior segmentor body, and a posterior part, or vertebral or neural arch. These twoparts enclose a foramen, the vertebral foramen. Together, the vertebralforamen of the vertebrae form a canal for the protection of the spinalcord. The vertebral arch consists of a pair of pedicles and a pair oflaminae.

The body is the largest part of a vertebra, and is more or lesscylindrical in shape. Its upper and lower surfaces are flattened. Infront, the body is convex from side to side and concave from abovedownward. Behind, it is flat from above downward and slightly concavefrom side to side. The pedicles are two short, thick processes, whichproject backward, one on either side, from the upper part of the body,at the junction of its posterior and lateral surfaces.

Over the years, various techniques and systems have been developed forcorrecting spinal injuries and/or degenerative spinal processes. Spinalcorrection frequently requires stabilizing a portion of the spine tofacilitate fusing portions of the spine or other correctionmethodologies. Medical correction of this type is frequently employedfor many spinal conditions, such as, for example, degenerative discdisease, scoliosis, spinal stenosis, or the like. Frequently, thesecorrections also require the use of implants, such as, bone grafts.Stabilizing the spine allows bone growth between vertebral bodies suchthat a portion of the spine is fused into a solitary unit.

Several techniques and systems have been developed for correcting andstabilizing the spine and facilitating fusion at various levels of thespine. In one type of system, a rod or more commonly, a pair of rods isdisposed longitudinally, lateral to each side of the spine and adjacentalong the length of the spine in the region of concern. The rod isarranged according to the anatomy and the correction desired. In thissystem, the rod is aligned along the spine and engages various vertebraealong its length. The rod or rods engage opposite sides of the spineusing fixation elements, such as anchors, attached to vertebral bodiesby a bone screw that is inserted into the pedicle and penetrates intothe body of the vertebra.

Anatomy and correction frequently require aligning the rod and screw atvarious angles along the length of the portion of correction. In orderto provide this alignment, polyaxial screws/anchors have been developed.Many variations of bone screw and rod fixation systems exist on themarket today. However, prior systems have been limited in the amount ofangulation permitted relative to the place of attachment to the spine.In extreme cases, even with polyaxial screws, the spinal stabilizationrods may diverge in their orientation in not just one, but two or eventhree planes. Such divergence makes connection of the rods difficult.Stated another way, prior cross connector systems typically provided aconnector rod that was attached to and extended from the spinal supportrods perpendicularly. When the spinal support rods were non-parallelrelative to each other, as is often the case, the cross connector systemwould typically require an additional mid-spine connector piece to joinconnector rods extending from opposing support rods approximately overthe spine. Utilization of such a connector may require the excising ofbone to prevent the spinous process of the spine from interfering withplacement of the mid-spine connector. Additionally, such connectionsystems have required multiple components requiring multiple assemblysteps during surgery. Also, prior systems have involved the securing ofa screw assembly to a cross connector or spinal support rod by directcontact between a set screw and the rod. This contact causes subtledamage to the rod caused by plastic deformation of the rod by the setscrew.

Therefore, there is a need for a spinal cross connector assembly thatpermits a wide range of angulation of spinal support rods relative tothe spine and each other while providing an effective and secure lock ofthe cross connector and rod in the desired position. There is also aneed for a mechanism of attachment of spinal stabilizer or support rodsto each other that minimizes the possibility of damage by a set screwsecuring the cross connector to the support rods.

SUMMARY OF THE INVENTION

It is, therefore, an aspect of the present invention to provide aconnector device for a spinal stabilization apparatus that provides anincreased amount of allowable angulations between spinal stabilizer rodson opposing sides of the spine.

In addition, it is another aspect of the present invention to provide aspinal cross connector assembly that provides a mechanism of attachmentof spinal stabilizers or support rods to each other without the spinalstabilizers or support rods sharing a plane of orientation along theaxes of the rods.

It is still another aspect of the present invention to provide a crossconnector system that utilizes attachment mechanisms that minimize thepossibility of damage to the rod by a set screw securing the crossconnector to the support rod.

It is still another aspect of the present invention to provide a crossconnector that provides a simple method of attachment of opposingsupport rods located on either side of a spine.

In general, one embodiment of the present invention provides a connectordevice for a spinal stabilization apparatus that comprises a firstelongated portion adapted to engage at least a first spinal stabilizerrod proximal to the first end of the elongated portion. The first end ofthe first elongated portion may comprise a hook shape and a firstferrule and may engage the first spinal stabilizer rod up to about 20degrees from perpendicular to the first spinal stabilizer rod in anydirection. The ferrule can be adapted to be seated within the hook shapeof the first elongated portion. The edges of the hook shape may also bechamfered to permit angulation of the spinal support rod. The connectordevice may also include a second elongated portion which may comprise asecond hook shape and a second ferrule. The second elongated portion mayengage a second spinal stabilizer rod up to about 20 degrees fromperpendicular to the second spinal stabilizer rod in any direction. Theedges of the second hook shape may be chamfered to permit angulation ofthe second spinal stabilizer.

The ferrule is adapted to be seated within the first and/or second hookshape and is further adapted to engage the first and/or second spinalstabilizer rod, respectively. The first and/or second hook shapes maycomprise two opposed tabs separated by a first gap which forms anentrance into a channel of the hook shape. The ferrule may have anoutside diameter that is greater than the width of the first gap.Optionally, the ferrule may additionally have an outward extension orlug which extends outwardly from the surface of the ferrule to engage achamber or seat in a corresponding portion of the inner surface of thehook shape. The first and/or second elongated portion may additionallycomprise a retainer, such as a spring, for maintaining the ferrule incontact with one or more side walls of the hook shape proximal to thefirst gap. The first and/or second elongated portion may additionallycomprise an aperture, through which a set screw may be inserted toengage the ferrule and secure it in place.

A connector device for a spinal stabilization apparatus may additionallycomprise an elongated cross connector member affixed to the firstelongated portion on a first end of the cross connector member andaffixed to the second elongated portion on a second end of the firstelongated cross connector member. Alternatively, the first elongatedportion may additionally comprise a first elongated cross connectormember and the second elongated portion may additionally comprise asecond elongated cross connector member. In such an embodiment, theconnector device may additionally comprise a centerpiece adapted toconnect the first elongated cross connector member and the secondelongated cross connector member.

In some embodiments of the connector device, the first elongated portionand the second elongated portion are directly attached. In one suchexample, the first elongated portion and the second elongated portionare directly attached such that the first and second spinal stabilizerrods may be inserted into the connector device in an essentiallyparallel configuration relative to each other. In another example, thefirst elongated portion and the second elongated portion are directlyattached such that the first gap and the second gap are contiguous.

The connector device described herein may be used in a method oftreating a patient. The method may comprise attaching at least a firstlongitudinal spinal stabilizer and a second spinal stabilizer to thespine of a patient, and attaching a connector device as described to thespinal stabilizer. The first elongated member may have first and secondends, and the first spinal stabilizer is engaged to the first end of thefirst elongated member. The first and/or second end of the elongatedmember may be adapted to engage the first longitudinal spinal stabilizerwithin about 20 degrees of perpendicular to the first longitudinalspinal stabilizer in any direction. The first and/or second end of thefirst elongated member comprise a hook shape and a ferrule. The ferruleis adapted to engage a spinal stabilizer rod and to be seated within thehook shape.

The hook shape comprises two opposed tabs or extensions separated by afirst gap which forms a lateral entrance into a channel of the hookshape. The ferrule may have an outside diameter that is greater than thefirst gap. A spring or other retainer may be present in the first end ofthe first elongated member for maintaining the ferrule in contact withone or more side walls of the hook shape proximal to the first gap.

In the method of treating a patient the second elongated portion of theconnector device may be directly attached to the first elongated member.The first elongated portion and the second elongated portion may bedirectly attached such that the first and second spinal stabilizer rodsmay be inserted into the connector device in an essentially parallelconfiguration relative to each other. In another example of the method,the first elongated portion and the second elongated portion may bedirectly attached such that the first gap and the second gap arecontiguous.

Additionally in the method, the second elongated portion may be similarto the first elongated member or may be separate and have first andsecond ends. The second elongated portion may be adapted to engage thesecond longitudinal spinal stabilizer within about 20 degrees ofperpendicular to the second longitudinal spinal stabilizer in anydirection. The first end of the second elongated member or second end ofthe first elongated member may also comprise a hook shape. The first endof the second elongated member or second end of the first elongatedmember may include a ferrule adapted to engage the second spinalstabilizer, with the ferrule being adapted to be seated within the hookshape. The hook shape may comprise two opposed tabs separated by asecond gap which forms an entrance into a channel of the hook shape. Theferrule may have an outside diameter that is greater than the secondgap. The first end of the second elongated member may additionallycomprise a spring for maintaining the ferrule in contact with one ormore side walls of the hook shape proximal to the second gap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of one example of the polyaxial crossconnector of the present invention;

FIG. 1B is a partially exploded view of the embodiment shown in FIG. 1Afrom an alternate elevation;

FIG. 1C is a perspective view of another example of the polyaxial crossconnector of the present invention;

FIG. 1D is a perspective view of still another example of the polyaxialcross connector of the present invention;

FIG. 1E is a perspective view of a variation on the example of thepolyaxial cross connector of the present invention shown in FIG. 1D;

FIG. 2A is an exploded, perspective view of a hook end member of theembodiment of FIG. 1, as assembled;

FIG. 2B is an exploded view of the embodiment shown in FIG. 2A from analternate elevation;

FIG. 2C is an exploded view of the embodiment shown in FIGS. 2A and 2Bfrom an alternate elevation;

FIG. 2D is a cross sectional view of an alternate embodiment of thepolyaxial cross connector of the present invention;

FIG. 2E is a cross sectional view of a variation of the embodiment shownin FIG. 2D;

FIG. 2F is a cross sectional view of an alternate embodiment of thepolyaxial cross connector of the present invention utilizing analternate retainer;

FIG. 2G is a cross sectional view of another alternate embodiment of thepolyaxial cross connector of the present invention utilizing anotheralternate retainer;

FIG. 2H is an exploded, perspective view of a hook end member of anembodiment of the polyaxial cross connector which does not rely on thepresence of a spring or other retainer;

FIG. 3A is an exploded view of an embodiment of the polyaxial crossconnector of the present invention that utilizes a cross connectorportion instead of a separate cross connector rod;

FIG. 3B is a perspective view of the embodiment shown in FIG. 3A;

FIG. 4 is an exploded view of an embodiment of the polyaxial crossconnector of the present invention in which the first and secondelongated members are directly attached;

FIG. 5A is an exploded view of an alternate embodiment of the polyaxialcross connector of the present invention in which the first and secondelongated members are directly attached and form a single contiguousgap;

FIG. 5B is a perspective view of the embodiment shown in FIG. 5A;

FIG. 5C is a perspective view of the embodiment shown in FIGS. 5A and 5Bshown from an alternate elevation.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed toward a spinal stabilizationapparatus for connecting and immobilizing spinal support rods locatedlaterally on opposite sides of a section of a spine. In one embodiment,the apparatus includes first and second hook members. The first hookmember is adapted to engage a first longitudinal spinal supportstabilizer located laterally to a first side of a section of a spinalcolumn, and the second hook member is adapted to engage a secondlongitudinal spinal support stabilizer located laterally to a secondside of a section of a spinal column. Each of the first and second hookmembers may also be adapted to engage opposite ends of a cross connectorrod. Alternatively, the first and second hook members may be attached toeach other. That is, the first and second hook members are located onopposite ends of a single elongated member. First and second hookmembers may be further adapted to permit angulation of an attachedspinal support rod relative to the hook end member. Stated another way,first and second hook end members may be adapted to attach to a spinalsupport rod at an angle of between about 70 and 90 degrees in anydirection, i.e., through an arc of about 40 degrees in any directioncentered on a perpendicular attachment to the spinal support rod.

In another embodiment, the first and second hook end members may beadapted to attach to a spinal support rod at an angle between about 75and 90 degrees, that is, through an arc of about 30 degrees in anydirection centered on a perpendicular attachment. In still anotherembodiment, the first and second hook end members may be adapted toattach to a spinal support rod at an angle between about 80 and 90degrees, that is, through an arc of about 20 degrees in any directioncentered on a perpendicular attachment.

The following examples should not be viewed as limiting the scope of theinvention. The claims will serve to define the inventions. Additionally,it should be noted that elements of one example may be combined withelements of another example, except where the function of the componentsprohibits such combination. The following examples are non-limitingtherefore in their arrangements and combinations of elements.

As shown in FIGS. 1A and 1B, a spinal stabilization apparatus 10includes first 12 and second 14 hook members. First hook member 12 isadapted to engage a first longitudinal spinal support stabilizer rod 16located laterally to a first side of a section of a spinal column, andthe second hook member 14 is adapted to engage a second longitudinalspinal support stabilizer rod 18 located laterally to a second side of asection of a spinal column. Each of the first and second hook members12, 14 are also adapted to engage opposite ends of a cross connector rod20, which is secured in first and second hook members 12, 14 by setscrews 22.

FIGS. 2A, 2B and 2C illustrate an arrangement of the first hook member12. It should be understood, however, that similar or identicalstructures and components may also be present in second hook member 14.Hook member 12 is an elongated structure with a hook end 32 and crossconnector end 34 on opposite ends of hook member 12. Hook end 32 may begenerally described as hook shaped, comprising a hook end channel 36passing through the hook shape and entering into a generally sphericalcavity 37.

Hook member 12 (and also hook member 14) also includes a ferrule 24,which is C-shaped or generally spherical in shape with a generallycylindrical channel 26 located therethrough, creating an arcuate seat 28in the walls of channel 26 for receiving a stabilizer such as a rod 16.As a result of the presence of channel 26 in ferrule 24, the open end offerrule 24 includes two opposed tabs 40 located to each side of channel26. Tabs 40 may be configured in such a way that tabs 40 have a minoramount of flexibility, allowing them to flex outwardly as rod 16 isinserted into and passes into channel 26 and is ultimately secured inseat 28. Alternatively, the open end of ferrule 24 may be configuredsuch that rod 16 fits into channel 26 without requiring any movement oftabs 40. Channel 26 has a cross-sectional configuration that correspondsto the cross-sectional configuration of rod 16 (or rod 18) such thatarcuate seat 28 maintains contact with at least half of the portion ofrod 16 that lies within channel 26. In one embodiment, arcuate seat 28maintains contact with more than half of the circumference of rod 16that lies within channel 26. In another example, arcuate seat 28maintains contact with about two thirds or more of the circumference ofrod 16 that lies within channel 26. In this manner, any load to betransferred between rod 16 and hook end 32 is distributed as evenly aspossible across the length and width of seat 28.

Ferrule 24 is adapted to be seated within cavity 37 in hook end 32 suchthat rods 16, 18 may be engaged in ferrule 24 and pass through channel36. Channel 36 is generally cylindrical, with a gap 31 between hook tabs30 forming a lateral entrance into channel 36 and forming the hook shapeof hook end 32. Stated differently, channel 36 may be considered to bethe center of C-shaped ferrule 24. Gap 31 is configured to allow rods16, 18 to pass through gap 31 into channel 36, such that ferrule 24makes contact with at least some portion of side wall 46 of hook member12, 14. In some embodiments, gap 31 is essentially the same distance asthe diameter of rods 16, 18. In other embodiments, gap 31 is up to 0.1mm larger than the diameter of rods 16, 18. Ferrule 24 may be furtherconfigured to allow it to be inserted into cavity 37 through channel 36but with an outside diameter that prevents it from passing through gap31.

In another embodiment, as shown in FIG. 2D, ferrule 24 may have a lug 53extending outwardly from the outer surface of ferrule 24. Lug 53 isadapted to engage or at least project into a corresponding seat 44located in the inner surface of hook member 12, 14 created by cavity 37.Seat 44 may be larger than lug 53 to permit adjustment of the positionof ferrule 24 and rod 16 inserted into ferrule 24. In one particularembodiment, lug 53 is a frustoconical projection from the outer surfaceof ferrule 24 (FIG. 2D). In another embodiment, lug 53 is generallyrectangular in shape and may have rounded edges (FIG. 2E).

In one example, ferrule 24 has an outside diameter of about 6.5 mm,cavity 37 has a diameter of approximately 6.5 mm, gap 31 is about 5.5 mmwide and the diameter of rods 16, 18 is about 5.5 mm. This provides forthe insertion of ferrule 24 into cavity 37 and for the insertion of rods16, 18 into seat 28 of ferrule 24 through gap 31 but prevents ferrule 24from passing through gap 31.

Channel 36 may be further adapted to permit rotation of ferrule 24within channel 36 and thereby allow angulation of spinal support rod 16,18 within channel 36. One possible adaptation is the presence ofchamfered edges 38 surrounding channel 36, allowing ferrule 24 and rod16, 18 to pivot within channel 36. In one embodiment, rod 16, 18 iscapable of pivoting through an arc of approximately 40 degrees in anydirection. Stated another way, hook members 12, 14 are adapted to attachto a spinal support rod at an angle of between about 70 and 90 degreesin any direction, i.e., through an arc of about 40 degrees in anydirection centered on a perpendicular attachment to the spinal supportrods. In another embodiment, hook members 12, 14 are adapted to attachto a spinal rod at an angle of between 75 and 90 degrees in anydirection, that is, through an arc of about 30 degrees in any directioncentered on a perpendicular attachment. In another embodiment, hookmembers 12, 14 are adapted to attach to a spinal rod at an angle ofbetween about 80 and 90 degrees in any direction, that is, through anarc of about 20 degrees in any direction centered on a perpendicularattachment. In still another embodiment, hook members 12, 14 are adaptedto attach to a spinal rod at an angle of between 85 and 90 degrees inany direction, that is, through an arc of about 10 degrees in anydirection centered on a perpendicular attachment.

Hook end 32 may also include a retainer such as spring 42 formaintaining ferrule 24 in channel 36 by keeping ferrule 24 in contactwith side wall 46 of cavity 37. As mentioned above, ferrule 24 may beconfigured such that it can not pass through gap 31. Spring 42 may beseated in a seat 44 within cavity 37 either in the absence (FIGS. 2A-2C)or in the presence (FIG. 2D) of lug 53. It should also be noted thatwhen lug 53 is present, spring 42 is not required to be located over lug53 as shown in FIG. 2D. It is also possible for spring 42 to be separatefrom lug 53. For example, spring 42 may be located within set screw 48,as shown in FIG. 2E.

It is also envisioned that other resilient components may be used inplace of spring 42. For example, a retainer may take the form of aresilient, flexible tab projecting from the inner wall of cavity 37 (notshown). Alternatively, a Belleville washer (56, FIG. 2F) or a curledspring (58, FIG. 2G) may also be used as a retainer. Hook members 12 and14 also each contain a set screw aperture 50, which passes through hookmember 12 and accesses cavity 37, allowing set screw 48 to contactferrule 24. Set screw 48 may have a flat surface where it contactsferrule 24 or washer 56 (FIG. 2F) or it may have a concave surface whichgenerally corresponds to the shape of ferrule 24 (FIG. 2G). It shouldalso be noted that the presence of a retainer is optional. An embodimentthat does not rely on the use of spring or other retainer is provided inFIG. 2H.

Cross connector end 34 of hook members 12, 14 comprises a cavity 50adapted to receive cross connector rod 20. As in the embodiment shown,cavity 50 may be enclosed on three sides to allow cross connector rod 20to be inserted into cavity 50 and engage hook member 12 at crossconnector end 34. Cavity 50 may also include threads 52 to engage a setscrew 54. When cross connector rod 20 is inserted into cavity 50, setscrew 54 contacts cross connector rod 20 and secures it in place incross connector end 34.

It is envisioned that cross connector rod 20 may take any of a number ofconfigurations. Cavity 50 may also be appropriately configured wherenecessary to accept rod 20. For example, cross connector rod 20 may notonly be cylindrical, as shown in FIGS. 1A and 1B, but rod 20 may alsohave a flat upper surface as shown in FIG. 1C, to permit wider contactbetween rod 20 and set screws 22.

It is further envisioned that a cross connector rod may form a singleunitary component with hook member 12, 14. For example, cross connectorportion 120 of hook member 12 may be hemicylindrical in shape with aflat surface facing upward as shown in FIG. 1D. In such an embodiment,cross connector portion 122 of hook member 14 may be hemicylindrical inshape with a flat surface facing downward. Where cross connectorportions 120 and 122 overlap, together they form a cylindricalstructure, and which may be secured together at a centerpiece 60 whichhouses a set screw 62, by tightening set screw 62 and immobilizing eachof cross connector portions 120 and 122 against each other and/orcenterpiece 60. Portions 120 and 122 may also be oriented withcomplementing vertically oriented flat surfaces as shown in FIG. 1E.

As mentioned above, ferrule 24, cavity 37 and channel 36 are adapted topermit rod 16 to pivot within channel 36. In one embodiment, rod 16 iscapable of rotating through an arc of approximately 40 degrees in anydirection. Likewise, the identical structures in second hook member 14permit rod 18 to be angulated through an arc of approximately 40 degreesin any direction, with the arc centered on a perpendicular attachment.Stated another way, rods 16, 18 may be angulated through hook members12, 14 not only side-to-side, or up-and-down relative to the centralaxis of hook members 12, 14, but both side-to-side and up-and-downsimultaneously. In this way, support rods 16 and 18 may be angled atotal of up to 40 degrees from parallel in any direction while stilldirectly connecting the first and second hook members 12, 14 with asubstantially straight cross connector rod 20. In those situations whererods 16 and 18 are angled more than 40 degrees from parallel to eachother, a connection may still be directly made between first and secondhook members 12, 14 with a single cross connector rod 20. In such acase, cross connector rod 20 may be bent with an instrument for bendingspinal rods, such as an instrument known in the art as a French Bender(not shown), to accommodate the greater angulation. Therefore, even incases where there is greater than 40 degrees of angulation in anydirection, relative to a parallel condition between the rods, thepresent invention provides an apparatus and method for spinalstabilization utilizing only a single cross connector rod without theneed for an intervening connector piece located between the hookmembers, thereby directly connecting hook members 12 and 14 without anintervening connector. The absence of an additional connector other thanthose directly connected to the spinal support rods, i.e. hook members12 and 14, permits spinal stabilization with a decreased or eveneliminated need for excision of bone, such as the spinous process, topermit installation of the stabilization system.

As mentioned above, a spinal stabilizer device may include a first hookend and a second hook end as described above, with the exception of theabsence of a cross connector rod. That is, the device is of a fixedlength. One such embodiment is shown in FIGS. 3A and 3B. The spinalstabilizer device 110 comprises first hook member 112 and second hookmember 114, each of which is adapted to receive a C-shaped ferrule 24with a lug 53 and a spring 42 as described above. First hook member 112and second hook member 114 also each have a set screw aperture 50adapted to receive a set screw 48, which can be secured in aperture 50against ferrule 24, as also described above. In this embodiment,however, first hook member 112 and second hook member 114 are connectedby cross connector member 134. This embodiment is otherwise similar tothose embodiments described above.

One similar embodiment that may be particularly useful in the upperthoracic or lower lumbar regions eliminates cross connector member 134.As shown in FIG. 4, first hook member 112 and second hook member 114 aredirectly attached to each other. First and second hook members 112, 114are each adapted to receive a C-shaped ferrule 24 optionally having acylindrical lug 53, and additionally may have set screw apertures 50adapted to receive set screws 48. First and second hook members 112, 114may also comprise springs 42 for maintaining pressure on ferrules 24.

A further embodiment that may be used to secure two spinal stabilizerrods end-to-end is provided in FIGS. 5A-5C. As in previous embodiments,each of hook members 212, 214 may be generally described as hook shaped,comprising a hook end channel 136 passing through the hook shape andentering into a cavity 37. However, in the current embodiment, hook endchannel 136 is common to both first hook end member 212 and second hookend member 214. In previously described embodiments, first hook member12 and second hook member 14 are arranged such that stabilizer rods 16,18 are capable of being inserted into hook members 12, 14 in anessentially parallel position. In contrast, in this embodiment, hookmembers 212, 214 are aligned such that channel 136 forms a commonchannel of first hook member 212 and second hook member 214 into whichstabilizer rods 16, 18 are inserted. In this way, stabilizer rods 16, 18are inserted into a stabilizer apparatus 210 in an end-to-end alignment.This may be particularly useful where a patient's physiology requiresthat stabilizer rods 16 and 18 be angled relative to each other, such asin the obtuse relationship shown in FIGS. 5B and 5C.

As with previous embodiments, hook members 212, 214 each include aferrule 24, which is C-shaped or generally spherical in shape with agenerally cylindrical channel 26 located therethrough, creating anarcuate seat 28 in the walls of channel 26 for receiving a stabilizersuch as rods 16, 18. The open end of ferrule 24 again may include twoopposed tabs 40 located to each side of channel 26. Tabs 40 may beconfigured in such a way that tabs 40 have a minor amount offlexibility, allowing them to flex outwardly as rods 16,18 are insertedinto and pass into channel 26 and are ultimately secured in seat 28.Alternatively, the open end of ferrules 24 may be configured such thatrod 16 fits into channel 26 without requiring any movement of tabs 40.Channel 26 may have a cross-sectional configuration that corresponds tothe cross-sectional configuration of rods 16, 18 such that arcuate seat28 maintains contact with at least half of the portion of rod 16 thatlies within channel 26. In one embodiment, arcuate seat 28 maintainscontact with more than half of the circumference of rod 16 that lieswithin channel 26. In another example, arcuate seat 28 maintains contactwith about two thirds or more of the circumference of rod 16 that lieswithin channel 26. As with previous embodiments, any load to betransferred between rod 16 and hook end 32 is distributed as evenly aspossible across the length and width of seat 28.

Ferrules 24 are adapted to be seated within hook members 212, 214 suchthat rods 16, 18 may be engaged in ferrules 24 and pass through channel136. Channel 136 is generally cylindrical, with a gap 31 between hooktabs 30 forming a lateral entrance into channel 136 and forming the hookshape of hook members 212, 214. Gap 31 is configured to allow rods 16,18 to pass through gap 31 into channel 36, allowing ferrules 24 to makecontact with at least some portion of side wall 46 of hook member 212,214. Alternatively, the open end of ferrules 24 may be configured suchthat rod 16 fits into channel 26 without requiring any movement of tabs40. In some embodiments, gap 31 is essentially the same distance as thediameter of rods 16, 18. In other embodiments, gap 31 is up to 0.1 mmlarger than the diameter of rods 16, 18. Ferrules 24 may optionally befurther configured to have a lug 53 extending outwardly from the outersurface of ferrules 24. Lug 53 can be adapted to engage or at leastproject into a corresponding seat located in the inner surface of hookmember 212, 214 as in previous embodiments. Seat 44 may be larger thanlug 53 to permit adjustment of the position of ferrule 24 and rod 16inserted into ferrule 24.

Springs 42 may also be present, again for maintaining ferrule 24 inchannel 136 by keeping ferrule 24 in contact with side wall 46. Springs42 may be positioned in association with lug 53 (as in a previousembodiment) or separate from lug 53. For example, spring 42 may belocated within set screw 48 (FIG. 5A).

In use, the cross connector system of the present invention would beutilized after spinal stabilization rods 16, 18 have been secured to thespine using bone screws, such as pedicle screws. Hook members 12 and 14(or 112, 114, or 212, 214) would typically be partially assembled priorto surgery, with ferrule 24 positioned within channel 36 and held inplace by spring 42 or other similar structures, when present. Hookmember 12 would be attached to rod 16 by sliding hook member 12 over rod16 and positioning a portion of rod 16 within channel 26. As statedabove, ferrule 24 is oriented in cavity 37 such that channel 26cooperates with channel 36 of hook member 12 to permit alignment of rod16 or rod 18 through both ferrule channel 26 and hook end channel 36.When rod 16 is passed through gap 31 and inserted into ferrule 24 incavity 37, the resilience of spring 42 allows ferrule 24 to betemporarily and reversibly positioned upward into cavity 37, away fromside wall 46. This allows tabs 40 to flex outward as rod 16, 18 passesinto channel 26 becoming secured against arcuate seat 28. Once rod 16,18 is secured in seat 28 and pressure against spring 42 is released,spring 42 again applies pressure to ferrule 24, forcing it into contactwith side wall 46 and holding it in place there.

Once corresponding first and second hook members 12, 14 are attached tosupport rods 16, 18, cross connector rod 20 is then inserted into eachcavity 50 of cross connector end 34 of hook members 12, 14. When a crossconnector rod 20 is not present, as in the embodiments of FIGS. 3A-5C,this step may obviously be omitted. As mentioned above, the angulationof hook members 12, 14 relative to a perpendicular position on supportrods 16, 18, allows the use of a single cross connector rod 20 betweenhook members 12 and 14 without resorting to an additional connectorlocated between support rods 16, 18. This allows a surgeon to utilizefewer components in a spinal stabilization system than previouslyneeded. A surgeon may simply select a cross connector rod of appropriatelength to connect first and second hook members and bend it theappropriate amount if necessary. Once cross connector 20 is engaged incavity 50, a set screw 22 may be used to secure cross connector rod 20in cavity 50. Alternatively, the length of the cross connection betweenhook members 12 and 14 may be adjusted with the use of centerpiece 60,as shown in FIGS. 1D and 1E.

After cross connector 20 (when present) is secured in cavities 50 ofhook members 12, 14, any final adjustments to the angulation of rods 16and 18 may be performed and ferrule 24 may be permanently secured intoposition with a set screw 48 that is inserted into a set screw aperture50. In contrast with spring 42, set screw 48 keeps ferrule 24 inconstant contact with side wall 46 and does not allow ferrule 24 to moveupward into channel 36 away from side wall 46 even temporarily, therebysecuring rod 16, 18. The engagement of set screw 48 against ferrule 24results in ferrule 24 being locked in place with arcuate seat 28 atleast partially surrounding rods 16, 18. Set screw 48 does not however,directly engage rods 16, 18. Instead, pressure from set screw 48 isdistributed to ferrule 24 and locking pressure is exerted against arelatively large surface area of rods 16, 18 by arcuate seat 28. In thisway, set screw 48 does not etch or otherwise deform or damage rods 16,18 and the possibility of damage to rods 16, 18 during use is minimizedor eliminated.

Although it is envisioned that ferrule 24 would ordinarily bepermanently secured in place after cross connector 20 is secured incavities 50, such a sequence of assembly is not necessarily required.For example, in those situations where hook members 12 and 14 areattached to rods 16 and 18 in a substantially perpendicular position,set screw 48 could be utilized as described above to secure ferrule 24in place before cross connector 20 is secured in place. The presentspinal stabilization system may also be adjusted in place after setscrews 48 and 22 have been secured in place by loosening one or more setscrews, making the necessary adjustments and re-securing the set screwsin place.

The present invention provides a self-adjusting spinal stabilizationsystem. Ferrule 24 may rotate within cavity 37 to allow a particularangulation of hook members 12, 14 (or 112, 114, or 212, 214) as dictatedby the patient's anatomy until set screws 48 are fully engaged withferrule 24. This eliminates the need for separate adjustment of aconnector in the mid-spine region as with prior systems, which onlyallow a hook member to attach to a spinal support rod perpendicularly.

Based upon the foregoing disclosure, it should now be apparent that thepolyaxial cross connector assembly of the present invention will carryout the objects set forth hereinabove. It is, therefore, to beunderstood that any variations evident fall within the scope of theclaimed invention and thus, the selection of specific component elementscan be determined without departing from the spirit of the inventionherein disclosed and described.

I claim:
 1. A connector device for a spinal stabilization apparatus, thedevice comprising: a first elongated portion adapted to engage a firstspinal stabilizer rod proximal to a first end of the first elongatedportion, the first end of the elongated portion comprising a first hookshape formed by two opposed tabs separated by a first gap which forms anentrance adapted to allow the first spinal stabilizer rod to passlaterally through the entrance into a first cavity of the hook shape,wherein the first cavity of the hook shape is generally spherical agenerally spherical first ferrule received in the generally sphericalfirst cavity of the hook shape, and configured to be fixedly engagedwith the first spinal stabilizer rod using a first set screw, andwherein the elongated portion is adapted to engage and to be fixed tothe first spinal stabilizer rod up to about twenty degrees fromperpendicular to the first spinal stabilizer rod in any direction; and asecond elongated portion for engaging with a second spine stabilizer rodin a fixed arrangement, the second elongated portion comprising a secondhook shape formed by two opposed tabs separated by a second gap whichforms an entrance adapted to allow the second spinal stabilizer rod topass laterally through the entrance into a second cavity of the secondhook shape, the second elongated portion engaging with the firstelongated portion such that the first stabilizer rod and the secondstabilizer rod are disposed in a fixed arrangement with respect to eachother.
 2. The connector device of claim 1, the second elongated portioncomprising a second ferrule that is adapted to be seated within the hookshape and to engage the second spinal stabilizer rod.
 3. The connectordevice of claim 2, wherein the first ferrule has an outside diameterthat is greater than the width of the first gap.
 4. The connector deviceof claim 1, the second elongated portion adapted to selectably engageand disengage with the first elongated portion.
 5. The connector deviceof claim 1, the second elongated portion adapted to engage a secondferrule to be seated within the hook shape of the second elongatedportion and is further adapted to engage the second spinal stabilizerrod.
 6. The connector device of claim 5, wherein the second ferrule hasan outside diameter that is greater than the width of the second gap. 7.The connector device of claim 1, wherein the first ferrule comprises anintegral outward extension from the outer surface of the first ferrule,and the corresponding first elongated portion comprises a seat adaptedto receive the outward extension of the first ferrule.
 8. The connectordevice of claim 1, wherein the first elongated portion comprises aretainer adapted to maintain the first ferrule in contact with one ormore side walls of the hook shape of the first elongated portionproximal to the first gap.
 9. The connector device of claim 8, whereinthe retainer comprises a spring.
 10. The connector device of claim 1,the first set screw adapted to engage the first ferrule through anaperture in the first elongated portion.
 11. The connector device ofclaim 1, wherein the connector device additionally comprises anelongated cross connector member affixed to the first elongated portionon a first end of the cross connector member and affixed to the secondelongated portion on a second end of the first elongated cross connectormember.
 12. The connector device of claim 1, wherein the first elongatedportion additionally comprises a first elongated cross connector memberand wherein the second elongated portion additionally comprises a secondelongated cross connector member.
 13. The connector device of claim 12,additionally comprising a centerpiece adapted to connect the firstelongated cross connector member and the second elongated crossconnector member.
 14. The connector device of claim 1, wherein the firstelongated portion and the second elongated portion are directlyattached.
 15. The connector device of claim 14, wherein the firstelongated portion and the second elongated portion are directly attachedsuch that the first and second spinal stabilizer rods may be insertedinto the connector device in an essentially parallel configurationrelative to each other.
 16. The connector device of claim 14, whereinthe first elongated portion and the second elongated portion aredirectly attached such that the first gap and the second gap aredisposed co-linear along a same axis.
 17. A method of treating apatient, the method comprising: attaching at least a first longitudinalspinal stabilizer and a second longitudinal spinal stabilizer to thespine of a patient; and attaching a connector device according to claim6 to the first and second spinal stabilizers.
 18. The method of claim17, wherein the first elongated portion and the second elongated portionof the connector device are directly attached.
 19. The method of claim18, wherein the first elongated portion and the second elongated portionare directly attached such that the first and second spinal stabilizerrods may be inserted into the connector device in an essentiallyparallel configuration relative to each other.
 20. The method of claim18, wherein the first elongated portion and the second elongated portionare directly attached such that the first gap and the second gap aredisposed co-linear along a same axis.